A comparison of the shaping ability of four rotary nickel-titanium files in simulated root canals

Abstract

The purpose of this study was to compare the root canal shaping ability of 4 rotary NiTi instruments in sim-ulated root canals. For the preparation of thirty two curved root canals, Mtwo inst ruments using “single length”technique, andProfile, ProTaper Universal, and K3 using crown-down technique (N = 8) were used. All canal samples were pre-pared by reaching an apical canal size of #30. Pre- and post-in strumentation digital images were recorded and anassessment of canal shape was determined using a computer image analysis program SigmaScan Pro (SystatSoftware Inc., San Jose, CA, USA). The changes of the dimension of inner walls of canals, (2) the changes of thedimension of outer walls of canals, and (3) the centering ratio were measured at 7 measuring points, and thendata were statistically analyzed using one-way ANOVA and Duncan’s test. The results were as below; 1. The root canal shaping ability of Profile was significantly faster than that of other rotary NiTi instru-ments (p < 0.05).2. The deformation and fracture of all instruments used for this study were not experienced. 3. In the degree of changes of the dimension of inner walls of canals, Profile demonstrated the lowestchanges of the dimension of inner walls of canals except at the measuring points of the 1 and 2 mm (p <0.05). However, the ProTaper Universal showed the highest changes of the dimension of inner walls ofcanals at all measuring points (p < 0.05). 4. In the degree of changes of the dimension of outer walls of canals, Mtwo demonstrated the lowest changseof the dimension of outer walls of canals except at the measuri ng point of the 1 mm (p < 0.05). However,Profile exhibited the highest changes of the dimension of outer walls of canals at the measuring points of3 and 4 mm and ProTaper Universal and K3 showed the largest cha nges of the dimension of outer wallsof canals at the measuring points of 1, 2, 6, and 7 mm (p < 0.05). 5. In degree of centering ratio, Profile demonstrated the least centering ratio comparing with the centeringratio shown by other NiTi instruments at the measuring points of 1, 4, 5, and 6 mm.Results suggest that in the coronal part of canal preparation, active cutting files such as ProTaper Universalmay efficiently flare the canal orifice and form a better taper , and in the apical part of the canal, files whichhave a better centering ability such as Profile maymaintain the original canal curvature and reduce theshaping time.